In the design and production of prototype parts for articles of manufacture as well as for preparation of various thermal and electrical insulators, and also patterns, dies and molds for investment casting, during the past several decades there has arisen a number of systems and processes termed "rapid prototyping" or desk top manufacturing or free form manufacturing (FFM) or the like. A number of these systems primarily rely upon preparing sequential cross-sectional layers of the desired three-dimensional object with sequential cross-dimensional adjacent layers integrated together as successive laminae to fabricate the three-dimensional laminar-like structural object.
Illustrative of one such rapid prototyping method is that of fabricating three-dimensional objects by stereolithography, such as described in U.S. Pat. No. 4,575,330, C. W. Hull. That patent teaches a generating of three-dimensional objects by creating a cross-sectional pattern of the object to be formed at a selected planar surface of a fluid medium capable of having its physical state altered by impinging radiation or the like, for changing of the pattern on the fluid surface to a solid planar-like cross-section and then successively forming corresponding successive adjacent cross-sections of the object on top thereof with successively-created adjacent cross-sections integrated together into a laminar-like build-up of the desired object.
Additional rapid prototyping and desk-top manufacturing and the like systems are described, for example in "Mechanical Engineering", April 1991, pages 34-43, in a Special Report entitled "Rapid Prototyping Systems" and in the "Tool And Manufacturing Engineers Handbook", Fourth Edition, Volume VI, 1992, Chapter 7, pages 7-9 to 7-26, entitled "Rapid Prototyping".
Many of the taught systems now in commercial practice, or under development, produce resinous polymeric articles from liquid monomers or polymer powders involving technologies of laser induced polymerization, broad-spectrum light initiated photopolymerization, selective laser powder sintering and the like. Only two art systems appear to be applicable to free-forming a body of an inorganic substance, such as a ceramic or the like. One of these systems in forming layers, would selectively sinter directly a pattern on an inorganic powder surface by a laser, or would indirectly selectively sinter a pattern of a lower melting point binder material admixed with the inorganic powder, and then by repetition build-up sintered layers of the pattern into the object. Another system would use ink jet printing technology to bind a layer of ceramic particles together by selective application of a binding medium to the inorganic particles and by repetition build up cross-sectional layers into the formed body or structure. ("Proceedings of the Solid Free-Form Fabrication Symposium", Univ. of Texas, 1990, M. J. Cima and E. M. Sacks, "Three-Dimensional Printing: Form, Materials and Performance", p. 187-194).
Included in the just-described rapid prototyping and desk-top manufacturing systems for fabricating prototypes and other bodies are computer aided design (CAD) and computer aided manufacturing (CAM) technology. For example, in the just-mentioned U.S. Pat. No. 4,575,330, one may use various principles of computer generated graphics so as to produce designed three-dimensional objects directly from computer instructions. Thus, the sought structural body may be designed through CAD by a computer operator using computer-aided graphics and functions of the computer to design and/or sculpture a desired three-dimensional model or prototype body or the like whose image memory can be displayed on a computer screen (CRT) for subsequent review and modification, if desired. Thereafter, the computer through CAM can create mathematical sections or slices of the designed three-dimensional model of the object into successive adjacent cross-sectional layers, and by CAM instruct a making by a specific technology of the object represented by the image. For example, as taught by the aforementioned patent, CAM will cut the image of the CAD-designed body or prototype into multiple successive cross-sectional layers and issue the operating instructions and parameters for successively forming by stereolithography the successively adjacent cross-sectional layers one on top of another with the layers integrated into a laminar built-up structure of the desired body of polymerized resin.
Depending on the particular compositions and materials used in fabricating various bodies by the particular rapid prototyping, desk-top manufacturing or free-form manufacturing or like procedures, the various fabricated bodies are useful in a variety of applications. A natural application is the creation of a concept model so that a designed part can be touched and examined and reviewed for aesthetic purposes and possibly tested for its fit, its ergomatic feasibility and the like utility requisites. Where a limited production of several to a few models are needed, the economics of fabrication may be even more favorable than using more elaborate tooling for fabrication. Models and prototypes thus can be evaluated and their parameters and dimensions altered and finalized for further evaluation and testing of the altered bodies. Some other illustrative utilities for various generated bodies from various materials include: calcium phosphate and hydroxylapatite materials to generate customized bodies for orthopaedic hard tissue implants; solid-liquid porous filters of various particulate materials bound together by sintering after a burn-off removal of an initial fugitive adhesive binder; heat and electrical solid insulators; as well as ceramic cores and shells for metals casting and for other purposes from alumina with colloidal silica binders or of predominantly silica or refractory inorganic oxides; and the like.